Fire is a thermal reaction of three components i.e. oxygen, heat and a combustible material.

In fire fighting at least of one of these components has to be eliminated to stop the reaction.

Fires are divided into 5 different classes, depending on the type of combustible material.

fires of solid substances mainly of organic nature which normally burn by forming embers as for example coal, paper or textiles.

fires of liquids or liquefying substances like petrol or alcohol. Substances which liquefy at higher temperatures,  like wax, also form part of this group.

fires of different types of gases like ethyne, hydrogen or natural gas.

burning metals.

fires of edible fats and oils used in deep fat fryers, frying pans and other kitchen appliances. These fires require special extinguishing agents because of the high danger of a fat explosion. In such an explosion the water contained in the extinguishing agent suddenly evaporates and the burning fat is tossed out of the frying pan.